1. Field of the Invention
The invention relates generally to systems and methods used to flow drilling muds and to extract gas from such muds.
2. Description of the Related Art
A standard drilling process includes circulating drilling mud through a well to establish well control, cutting removal and bit cooling. When drilling through a medium containing gas, condensate or oil, the hydrocarbons are released from the penetrated interval. The released gas is then transported to the surface in the drilling mud. Additional gas may be released into the mud from the oil or condensate due to changing conditions from subsurface to surface. The amount of released gas, not bound or trapped in or on the cuttings, depends on the porosity, permeability and hydrocarbon saturation of the formation.
Mud logging is a commonly applied service in the hydrocarbon production industry and relates to extraction and measurement of hydrocarbons which are present in the drilling mud. Measurements are conducted at the surface during drilling operations with a mass spectrometer, a gas chromatograph, or a combination of both. Of particular relevance to the industry are the hydrocarbons which are released from the penetrated lithological units and recorded at the surface once they become evaporated into gaseous phase under atmospheric conditions. Ideally, the measured hydrocarbons are only from the milled formation and can, therefore, provide highly valuable information when correlated with the corresponding depth and corrected for artifacts like recycled connection and/or tripping gas.
Depending upon the mud and hydrocarbon combination, the amount of each hydrocarbon in solution or present in gas phase may vary. Conventional hydrocarbon extraction (C1 to C8) is accomplished by feeding mud through a vessel with a mechanical agitator and sucking the evaporated hydrocarbons from the headspace of the device (gas trap) towards the measuring unit. Based upon the measured hydrocarbon compositions and the fluid type used for the drilling operation (water-based mud, oil-based mud and synthetic oil-based mud) features like gas/oil contacts and oil/water contacts can be determined.